The number density of free electrons in copper is nearly $8 \times 10^{28}\,m ^{-3} . A$ copper wire has its area of cross section $=2 \times 10^{-6}\,m ^2$ and is carrying a current of $3.2\,A$. The drift speed of the electrons is $.....\times 10^{-6}\,ms ^{-1}$.
A$125$
B$124$
C$123$
D$122$
JEE MAIN 2023, Easy
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A$125$
a $n =8 \times 10^{28}\,m ^{-3}$
Area $=2 \times 10^{-6}\,m ^2$
$I=3.2\,A$
$I = neAv_{d }$
$V_{ d }=\frac{ I }{ neA }=125 \times 10^{-6}\,m / s$
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